For a debilitating disease as destructive as HIV, any amount of progress is an outright victory. Therefore, when a patient was declared to be in HIV-remission without the use of treatment in early March, the news was astounding. It is too soon to ascertain whether the patient is fully cured, but many are eager to praise the methods that were used to accomplish this result for only the second time in history. The first case was recorded nearly ten years ago in a man called The Berlin Patient. The current patient, a male from the UK, had been receiving antiretroviral therapy (ARV) for HIV in 2012 when he was diagnosed with advanced Hodgkin’s lymphoma, a cancer of the immune system. In conjunction with his chemotherapy, the patient received a hemopoietic stem cell transplant, which is used to replace bone marrow that has been destroyed by cancer or destroyed by the chemo and/or radiation used to treat the cancer. The stem cells were special, though, in that their donor had two mutant copies of an immune cell receptor named CCR5, which is used by the majority of HIV strains to bind and enter host cells. Individuals who are homozygous for this CCR5 allele are resistant to the HIV-1 virus strain that uses this receptor. Thus, as previously occurred in the Berlin patient, who underwent the same stem cell transplant by a homozygous CCR5-mutant donor, HIV was halted from rebounding in the new patient’s fresh immune system. Despite mild Graft-versus-host disease, in which the patient’s immune cells attacked the newly transplanted cells, the patient has been in remission for 18 months since ceasing ARV therapy such that the HIV virus is undetectable.
The most important conclusion from both the Berlin and UK patients is that the mutation of the CCR5 gene is effective in preventing the progression of the HIV virus. Unfortunately, specific conditions are required to create this genotype in those who do not already have the mutation. Both HIV patients now in remission were diagnosed with leukemia, and the destruction of their immune systems provided the opportunity for renewal through stem cell transplant, a risky procedure. Therefore, as explained by a British professor, Ravindra Gupta, the next step in research may be to explore how to knock out [the CCR5] receptor in people with HIV, which may be possible with gene therapy.